2. Magnetization Some magnetically neutral objects can be influenced by magnetic fields Examples: carbon, copper, nickel Such objects are magnetized by an applied magnetic field Objects can be thought of as being made of magnetic dipoles Image obtained from: http://www.first4magnets.com/images/iron-filings-80g-science-education-x1-container-p3818-4109_zoom.jpg

3. Dipoles and Magnetic Fields Magnetic dipole Pair of opposite poles separated by a very small distance Random orientation under normal conditions

4. Dipoles and Magnetic Fields Magnetic dipole Pair of opposite poles separated by a very small distance Random orientation under normal conditions Reorient themselves when placed in an applied magnetic field—magnetization B applied

5. Dipoles and Magnetic Fields Magnetic dipole Pair of opposite poles separated by a very small distance Random orientation under normal conditions Reorient themselves when placed in an applied magnetic field—magnetization B applied

6. Dipoles and Magnetic Fields B applied Magnetizing substance with magnetic dipoles induces a counter-magnetic field All (N) pointing same way All (S) pointing same way Resultant magnetic field less than applied magnetic field B effective = B applied - B magnetization B magnetization

7. Permeability and Diamagnetism Permeability– ability of a magnetic field to apply force to a moving charge or current within a medium Permeability of free space– permeability within a vacuum μ 0 : 1.26 x 10 -6 Tm/A Permeability varies depending on substance– diamagnetism Permeability of diamagnetic– μ μ = μ r μ 0 μ r : relative permeability B applied B magnetization B effective

8. Permeability and Diamagnetism I2I2 I1I1 B2B2 ( )

9. Permeability and Diamagnetism I2I2 I1I1 B2B2

10. Magnetization Field